|
Inside the Real-time v$
Wait Events
The foundation concept of the ASH
architecture is called the time model, and Oracle10g has
introduced several important wait event
v$
views. Table 16.4 below shows some
v$ equivalents to
dba_hist views.
|
v$ View |
dba_hist View |
|
v$active_sess_hist
|
dba_hist_active_sess_history
|
|
v$sys_time_model
|
dba_hist_sys_time_model
|
|
v$active_session_history
|
dba_hist_active_sess_history
|
|
v$event_histogram
|
No equivalent DBA view |
Table
16.4:
Oracle
v$ equivalents to
ASH wait event tables
The main components of OWE interface are the
dynamic performance views:
v$session
_wait
;
and
v$session_event
as shown in Figure
16.8.
Figure
16.8:
The v$ event structures in
Oracle10g
These
v$ views are in-memory structures that feed data to the
ASH tables which provide time-series wait event information.
The ASH samples for wait events every second
and tracks the waits in the new
v$active_sess_hist
view. Before
looking into the wrh$
and ASH tables, it will be useful to take a quick tour of the
important v$ wait
event views.
SEE CODE DEPOT FOR FULL SCRIPTS
 |
This is an excerpt from my latest book "Oracle
Tuning: The Definitive Reference".
You can buy it direct from the publisher for 50%-off and get
instant access to the code depot of Oracle tuning scripts: |
http://www.rampant-books.com/book_1002_oracle_tuning_definitive_reference_2nd_ed.htm
|
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